diff --git a/src/js/db.js b/src/js/db.js
new file mode 100644
index 0000000..3e40ccb
--- /dev/null
+++ b/src/js/db.js
@@ -0,0 +1,63 @@
+class Db {
+	constructor() {
+		this.db = null;
+		this.dbName = "tinysub";
+		this.dbVersion = 3;
+	}
+
+	async open() {
+		if (this.db) {
+			return this.db;
+		}
+
+		const db = await this._openDatabase();
+		return db;
+	}
+
+	async _openDatabase() {
+		try {
+			return await new Promise((resolve, reject) => {
+				const req = indexedDB.open(this.dbName, this.dbVersion);
+
+				req.onsuccess = () => {
+					this.db = req.result;
+					resolve(this.db);
+				};
+
+				req.onerror = () => reject(req.error);
+
+				req.onupgradeneeded = (e) => {
+					const db = e.target.result;
+					const oldVersion = e.oldVersion;
+
+					// 1 -> 2: create queueStorage
+					if (oldVersion < 2 && !db.objectStoreNames.contains("queueStorage")) {
+						db.createObjectStore("queueStorage");
+					}
+
+					// 2 -> 3: create apiCache and cacheMetadata
+					if (oldVersion < 3) {
+						if (!db.objectStoreNames.contains("apiCache")) {
+							db.createObjectStore("apiCache");
+						}
+						if (!db.objectStoreNames.contains("cacheMetadata")) {
+							db.createObjectStore("cacheMetadata");
+						}
+					}
+				};
+			});
+		} catch (err) {
+			console.error("[Db] Failed to open IndexedDB:", err);
+			return null;
+		}
+	}
+
+	close() {
+		if (this.db) {
+			this.db.close();
+			this.db = null;
+		}
+	}
+}
+
+const db = new Db();
diff --git a/src/js/queue-storage.js b/src/js/queue-storage.js
index 3f7b652..18a8408 100644
--- a/src/js/queue-storage.js
+++ b/src/js/queue-storage.js
@@ -1,35 +1,8 @@
 // queue storage that persists to IndexedDB across sessions
 
 class QueueStorage {
-	constructor() {
-		this.db = null;
-	}
-
 	async ensureDB() {
-		if (this.db) return this.db;
-
-		try {
-			return await new Promise((resolve) => {
-				const req = indexedDB.open("tinysub", 2);
-
-				req.onsuccess = () => {
-					this.db = req.result;
-					resolve(this.db);
-				};
-
-				req.onupgradeneeded = (e) => {
-					const db = e.target.result;
-					if (!db.objectStoreNames.contains("queueStorage")) {
-						db.createObjectStore("queueStorage");
-					}
-				};
-
-				req.onerror = () => resolve(null);
-			});
-		} catch (error) {
-			console.error("[QueueStorage] IndexedDB initialization failed:", error);
-			return null;
-		}
+		return await db.open();
 	}
 	async save(songs, queueIndex) {
 		const db = await this.ensureDB();